The bean plant is gaining height and bending toward the sunniest spot of the window. This is an example of phototropism, a hormonal response to light that alters the direction of plant growth. Under this process, auxin in the apical meristem builds on the shadier side of the stem, causing cells to expand and the plant to bend in the opposite direction, towards the light.
A closer image of the plant displays the leaves, including their opposite arrangement and netted venation. From this perspective, the underside of the leaf, the lower epidermis, is visible. Between this layer and the upper epidermis are the spongy and palisade mesophyll, which contain the chloroplasts. The final top layer is the waxy cuticle, which functions in reducing water loss from the leaf.
